FORMATION OF LARGE-SCALE CROSS-BEDDING IN A CARBONATE UNIT

The type Lindsey Bridge Member of the Moorefield Formation of northeastern Oklahoma consists of 24 ft. of massively cross-bedded limestone. Cross-bed shape, lithologic variation, grain size and sorting, distribution of insolubles, and distribution of fossils and fossil burrows can be explained with reference to a hydrodynamic model developed in recent flume studies. Three facies can be distinguished in this unit: (1 Thei) foresets, thick-bedded, well-sorted, fine to medium crinoidal grainstones, dipping at angles up to 1° (2) toesets, which are thin-bedded, poorly sorted, skeletal packstones notably more fossiliferous than the foresets, with which they are laterally gradational; toesets dip at approximately 5°-8° (3) bottomsets, composed of argillaceous, fine-grained (mainly silt-size), skeletal limestones. Foresets overlie previously deposited bottomsets; this geometry is typical of regressive sedimentation. The exposure is adjacent to a pre-Moorefield topographic high. As currents crossing this high entered a basin on the downcurrent side, flow separation occurred. Bed material load was deposited mainly on the foreset slope, suspension material mainly in toeset and bottomset areas. The poor sorting of the toesets is in part due to reverse circulation, formed by the flow separation, which transported bottomset sediment back toward the foreset. Jopling (1965b) has shown that this depositional geometry produces tangential cross-beds similar to those seen in this outcrop. Differential settling velocity, substrate stability, and abundance of organic detritus influenced other sedimentologic properties of the deposit.     

LESSONS FROM A FEASIBILITY STUDY FOR COMPUTER MODELS OF COAL-BEARING DELTAS

A computer-generated model of a coal-bearing delta would be desirable if it included enough detail to reproduce the cyclical nature of the sediments. At the present stage of development of computers, and with the present state of knowledge of the quantitative aspects of transportation and sedimentation, it is not yet possible to set up such a model. However, the logical arrangement in a flow-diagram of the processes and parameters involved in delta formation strongly suggests that cyclical sedimentation can occur without the need for an external cyclical cause, such as tectonic or climatic oscillations. Attempts to provide for appropriate checks of a computer model bring out overall regularities in the assemblages of cyclic types in three different coal basins.     

Geordnete Deponie von festen Siedlungs- und geeigneten Industrieabfällen

Ohne Zusammenfassung     

Fracture induced emission of alkali atoms from feldspar

Emission of neutral atoms (K and Na) and molecules (H₂O and KOH) observed during fracture of K-feldspar have been accounted for by two independent mechanisms. H₂O and KOH emissions are attributed to the venting of fluid-filled inclusions, while emission of atomic K is due to surface effects accompanying cleavage of crystalline feldspar. The intensity of emitted potassium, at least 6 × 10¹⁴ atoms/cm² of surface area, is sufficient to affect K activities in solution during microbrecciation in the presence of rock-dominated fluids.